The invention pertains generally to a plug-and-socket connection for water-cooled, current-carrying lines, in particular, for bipolar high-frequency current conductors for the induction heating of tools.
In various industrial branches, the induction energy produced by an alternating current flowing through induction coils is used for heating electrically conductive components or ferromagnetic components. One such example is an induction welding torch. When using inductive heating, it is usually required to continuously cool the current-bearing lines in order to prevent overheating during operation of the respective device. In addition to air cooling systems, water cooling systems are also utilized quite frequently for this purpose.
There also exist automated tools, or tools actuated with the aid of robots, which contain current-bearing lines that need to be continuously cooled, preferably with water, during operation of the tool.
For example, a tool for automatically placing fastening bolts on supporting surfaces is described in DE 196 38 521 and in the corresponding PCT publication WO 98/12016. Each fastening bolt to be processed consists of a bolt shaft, one end of which is rigidly connected to a disk plate. The end face of the disk plate is coated with a dry hot-melt adhesive that can be reactivated under the influence of heat. The fastening bolts are fed to the tool from a stockpile via a separating device through a laterally extending supply channel. When the tool is actuated, the fastening bolts are individually transported to the mouthpiece from a standby position in such a way that the end face of the disk plate that carries the hot-melt adhesive points forward. The bolt shaft of the fastening bolt can be simultaneously gripped by a pneumatically actuated plunger, centered and placed under pressure when the mouthpiece of the tool is pressed flat against a supporting surface to which the fastening bolts should be bonded. An induction coil is accommodated in the mouthpiece of the tool which surrounds the fastening bolt and, in particular, its disk plate. While the pneumatically actuated plunger presses the fastening bolt against the supporting surface, this induction coil is supplied with a relatively intense high-frequency alternating current. This causes an alternating magnetic field to be generated that also penetrates the fastening bolts and inductively heats the fastening bolt, and in particular, its disk plate, very rapidly such that the layer of hot-melt adhesive on it melts, i.e., reactivates. The connection between the disk plate of the fastening bolts and the supporting surfaces is produced once the hot-melt adhesive again solidifies. The lines that conduct the intense high-frequency induction current need to be continuously cooled with water during operation of this device.
In a tool of this type, it is unavoidable that after a certain operating time, adhesive buildup occurs, in particular, in the vicinity of the mouthpiece, that ultimately makes it necessary to replace the tool. In addition, these tools usually require maintenance at regular intervals, e.g., in order to remove lime deposits from the lines that convey the cooling water. Until now, this always required the disassembly and maintenance of the entire tool, or replacement of the tool with another tool. Accordingly, these maintenance procedures are expensive and time-consuming. Supply of the cooling water and high-frequency alternating current are realized in the form of spatially separated connections, or bulky connection boxes are used that contain the necessary connections and have an excessive space requirement. When it is necessary to perform maintenance or to replace certain components, time-consuming and complicated procedures are frequently required that utilize special wrenches. If tools of this type are used in automated production lines, the production sequence on the entire production line needs to be interrupted for the time-consuming procedure of replacing the tool or performing the required maintenance work.
In previous attempts to simplify and accelerate the replacement of such tools and, if possible, to limit tool replacement to certain parts of the respective tool, the water-cooled current conductors of the induction coils present a particular challenge because they need to satisfy stringent requirements with respect to tightness and disruptive strength. In addition, such tools should also have a high impact strength against external mechanical influences and be able to withstand intense temperature fluctuations without developing functional defects. Thus, there is a need in the art for a plug-and-socket connection provided on the tool that can survive multiple tool replacements.
Accordingly, the present invention is a plug-and-socket connection for water-cooled, current-bearing lines for tools and, in particular, automated tools. The plug-and-socket connection is able to concentrate the energy exchange of the induction generator on the inductor and can be rapidly and easily actuated. In addition, the plug-and-socket connection satisfies predetermined requirements with respect to safety, tightness and electrical disruptive strength.
The plug-and-socket connection includes a chamber, and ducts for the incoming cooling water which open into this chamber, and are respectively provided in the housing of the female element and in the housing of the male element of the plug-and-socket connection. The ducts are connected to one another in the interconnected state of the plug-and-socket connection, and the chambers are directly connected to a water tube that supplies and conveys away the cooling water. The backflow of the cooling water occurs via a direct connection between a water tube that supplies the cooling water to the male element of the plug-and-socket connection and a water tube that conveys the cooling water away from the female element, such that the direct connection bypasses their respective chambers. The plug-and-socket connection includes two contact sockets of an electric bipolar plug-and-socket connection mounted in the housing of the female element in bores provided adjacent to the ducts. The contact pins of the electric bipolar plug-and-socket connection, which project from the end face of the housing and correspond to the contact sockets, are mounted in the housing of the male element in bores provided adjacent to the ducts. The electric lines for the power supply are connected to the contact sockets and the contact pins, respectively, and are guided through the water tubes connected to the chambers that supply and convey away the cooling water.
Advantageously, a plug-and-socket connection is provided which makes it possible to simultaneously close or open the electric circuit for supplying power to an induction coil and the cooling water circuit. Another advantage of the present invention is that maintenance work on the corresponding tools or the replacement of a tool or parts thereof can consequently be carried out much more easily and quickly. Still another advantage of the plug-and-socket connection is that an ideal transport of the coolant for the current conductors along two separate paths is ensured. Yet another advantage is that the two poles lie close to one another such that damaging parasitic fields are minimized. Still yet another advantage is that coolant is utilized for cooling the electric plug-and-socket connection in order to minimize the thermal stress.
A further advantage of the present invention is that the incoming cooling water flows around the electric lines and through the ducts provided in the housing, as well as through the chambers. Consequently, the electric plug-and-socket connections arranged in the housing are also cooled before the cooling water is conveyed away in order to cool the induction coil. Still a further advantage of the present invention is that since the chambers and ducts provided for cooling purposes are bypassed during the backflow, the cooling water backflow cannot mix with the incoming cooling water in the plug-and-socket connection, and is able to cool off again rapidly.
According to one preferred embodiment of the invention, the chamber in the female element and that in the male element are respectively formed by a pot-shaped recess in the housing that is sealed toward the outside by a closure piece that seals the housing wall; this closure piece contains two openings, into which two metal sleeves are inserted in a sealed fashion. The shorter metal sleeve opens into the chamber and the longer metal sleeve extends through the chamber and into a bore in the housing section situated adjacent to the chamber that is aligned with the opening in question. Tubes for the supply and backflow of the cooling water are pushed onto the ends of the metal sleeves that project from the closure piece, and are secured thereon by means of clamps.
In the female element, the longer metal sleeve extends into the inner bore section of the aligned bore, which is defined by a step. In the male element, the longer metal sleeve projects a certain distance from the smooth, continuous bore; when interconnecting the plug-and-socket connection, this projecting end fits into the outer bore section of the aligned bore in the female element, which is defined by a step, and is sealed therein relative to the wall by a ring seal.
Integrally formed onto the housing of the male element is a tubular projection that extends by a short distance beyond the end of the metal sleeve that projects from the end face and the contact pins that also project from the end face. When interconnecting the plug-and-socket connection, this tubular projection fits over the end section of the female element housing that faces away from the closure piece, and is sealed relative to this end section of the housing by means of ring seals. Advantageously, reliable connection between the female element and the male element of the plug-and-socket connection is thus achieved.
Three ducts for the incoming cooling water are offset relative to one another by 120xc2x0, and are preferably provided in the housing of the male element and of the female element, with the ducts in the female element being aligned with the ducts in the male element in the interconnected state of the plug-and-socket connection. Two bores for the electrical contact sockets and for the electrical contact pins, which are also offset relative to one another by 120xc2x0, and one bore for the connections of the water backflow are respectively provided between the ducts. Advantageously, superior cooling of the electric lines and the connections is achievable.
The electric lines that are guided inside, respectively, the water tubes that supply and convey away the cooling water and the shorter metal sleeves that open into the chambers, preferably consist of six wires that are divided into two groups of three wires each which are respectively connected to the contact sockets and to the contact pins at the level of the chambers of the female element and of the male element.
It should be appreciated that the connection between the female element and the male element may be secured with a retaining ring that contains a bayonet lock or screw-type lock.
According to one preferred embodiment, a mounting ring is fitted into an annular groove on the periphery of the housing of the male element and of the female element, respectively, with the mounting rings making it possible to securely mount both elements on carrier plates.
Other features and advantages of the present invention will be readily appreciated, as the same becomes better understood after reading the subsequent description taken in conjunction with the accompanying drawings.